This invention relates to rotary disc valves for feeding fluid flow and/or pressure to a plurality of ports, in particular to valves performing a predetermined cycle of feeding operations, such as, for example, numerous cyclical inflating and deflating a plurality of pressure cells in an inflatable device.
A rotary disc valve for inflating and deflating pressure cells in a therapeutic sleeve is disclosed in U.S. Pat. No. 5,014,681, incorporated herein by reference. This rotary disc valve comprises two discs: a stator disc with fluid flow ports connectable to a compressor and to the pressure cells, and a rotary distributor disc, the two discs contacting sealingly along a planar interfacing surface perpendicular to the axis of rotation. The ports of the stator disc open at the interfacing surface. The rotary distributor disc has a plurality of U-channels and through-going windows also opened at the interfacing surface. The channels and windows are configured so that during rotation of the rotary distributor disc, the compressor flow is successively directed, through the appropriate ports, to inflate the corresponding pressure cells, which are then successively opened to die atmosphere, all this following a predetermined sequence.
JP 01145474 discloses a rotary disc valve with a similar function where the stator comprises two discs fixed with respect to each other, the stator discs slidingly contacting a rotor distributor disc disposed therebetween. The rotor disc has U-channels and through holes connecting the ports of the stator in various combinations during one turn of the rotor distributor disc.
U.S. Pat. No. 4,614,205 discloses a multiport rotary disc valve with a similar function of simultaneous interconnection of a plurality of conduits in accordance with a predetermined cycle. The stator and the rotary distributor in this rotary valve are assemblies each comprised of two parallel plates or discs. The rotary assembly is sandwiched between two parallel plates of the stator assembly. Crossover pipes extend between the rotor plates to form either U-channels or through-passages similar to the above-cited designs.
The known rotary disc valves are capable of performing one predetermined cycle (sequence) of connections between the stator ports. The connections may be varied in time by controlling the rotational velocity and position of the rotor, but their order is determined by the pattern of the channels in the rotor and the stator.
In accordance with the present invention, there is provided a multi-port rotary disc valve comprising a stator with a plurality of fluid flow ports and a rotary distributor with a plurality of channels arranged in a channel pattern. The channels are adapted to connect the ports between them and/or to the environment in a plurality of predetermined combinations, each combination being associated with an angular position of the rotary distributor with respect to the stator. A succession of such combinations performed during a full or partial unidirectional turn of the rotary distributor constitute a predetermined sequence. The rotary distributor comprises a rotor and a mask mounted movably thereon, accommodating the plurality of channels. The mask is adapted to change the channel pattern by changing its position with respect to the rotor, thereby enabling the disc valve to perform different predetermined sequences corresponding to different positions of the mask.
In a preferred embodiment the mask and the rotor are coaxial and co-rotatable discs driven by a reversible controllable electric drive. The rotary distributor is mounted rotatably relative to the stator in a first direction only, while the mask disc is mounted rotatably relative to the rotor disc in a second direction only, contrary to said first direction. Thereby, the rotary distributor rotates only when electric drive rotates in the first direction and the mask disc rotates relative to the rotor disc only when the drive rotates in the second direction.
In a further embodiment of the rotary disc valve, the rotor disc has two faces, at least part of the rotary distributor channels connecting them. The first face sealingly contacts with a face of the stator, the connections between the stator ports and the rotary distributor channels being performed via this face. The second face sealingly contacts with a face of the mask disc, and the mask disc changes the channel pattern by switching connections between those channels that exit at the second face.
The rotary disc valve used for inflating and deflating N cells comprises a central inlet port and N outlet ports disposed around the central port. The rotor disc has a feed channel configured so that, during one turn of the rotary distributor, it successively connects the central inlet port to each one of the outlet ports.
The rotary disc valve is also adapted for group exhaust of all N inflated cells. For this purpose, the rotor disc has N through windows connecting the first face to the second face, configured so that, in a predetermined angular position A of the rotary distributor with respect to the stator, the N through windows match the N outlet ports. The mask disc has a group exhaust channel configured so that, in a predetermined angular position B of the mask disc with respect to the rotor disc, the group exhaust channel is connected to all the through windows of the rotor disc. The group exhaust channel is her connectable to a source of vacuum such as the entry of a compressor or pump, thereby enabling a group evacuation of any volumes connected to the N outlet ports of the stator, provided the positions A and B are attained simultaneously.
Preferably, the rotary disc valve is adapted to work as a part of a computerized system for inflating and deflating in cycles N cells connected to the N outlet ports. The stator of the rotary disc valve has N through pressure openings each disposed adjacent to one of the outlet ports, and a pressure channel connecting the pressure openings to a pressure outlet. The rotor disc has a bypass channel configured so as to be able to connect, when rotated, anyone of the outlet ports to the corresponding adjacent pressure opening while keeping the rest pressure openings stopped, thereby enabling the measurement of pressure PC in a volume connected to anyone outlet port. Preferably, the bypass channel is disposed behind the feed channel with respect to the first direction of rotation, so that the bypass channel is connected to outlet port No. n when, the feed channel is between outlet port No. n+1 and outlet port No. n+2, where n is an ordinal number of an outlet port, n increasing in the first direction. The system comprises a sensor to measure the pressure P0 in the central inlet port, and a sensor to measure the pressure PC in the pressure outlet. The system is programmed to terminate the inflation of a given cell at a predetermined instant value of the pressure P0 in order to obtain a target established pressure PE in that cell, and the system is adapted to correct this instant value in a next cycle if the measured pressure PC in a current cycle is different from the target pressure PE.